There are broadly used as elastomers homopolymers of conjugated diene monomers such as 1,3-butadiene and isoprene, or copolymers of conjugated diene monomers with vinyl aromatic monomers copolymerizable with the conjugated diene monomers, such as styrene.
Such copolymers of conjugated diene monomers with vinyl aromatic monomers are unvulcanizable thermoplastic elastomers, and are used as a modifier for impact-resistive transparent resins, polyolefin or polystyrene.
However, polymers containing olefinic unsaturated double bonds have the problem of the weather resistance due to the reactivity of the double bonds, and are used within a limited range, for example, where the polymers are not exposed to solar light. In order to solve this problem, there are known copolymers which are partially or completely saturated by hydrogenating the double bonds in the polymers.
There have been reported various usual methods of hydrogenating polymers having olefinic double bonds, and the methods are roughly classified into the following two methods. A first method is a method involving using a heterogeneous catalyst such as a metal-carrying catalyst in which a noble metal catalyst such as platinum, palladium or rhodium is carried on carbon, silica, alumina or the like. A second method is a method involving using a homogeneous catalyst of a Ziegler catalyst using nickel, cobalt or the like, or an organometal compound of rhodium, titanium or the like; and there are known, for example, a hydrogenation method involving using a catalyst in combination of a compound of a periodic table group VIII metal, particularly nickel or cobalt, and a proper reducing agent such as an alkylaluminum compound, and a method involving using a catalyst in combination of a bis(cyclopentadienyl)titanium compound and a proper reducing agent such as an alkylaluminum compound and hydrogenating unsaturated double bonds of a conjugated dienic polymer (for example, see Patent Literatures 1 to 7).